1. Field of the Invention
The present invention relates to vehicle suspensions and, more specifically, to farm vehicle suspensions which enable a farm vehicle to negotiate very rough and uneven ground.
2. Description of the Prior Art
Off road vehicles, and in particular farm vehicles, have to negotiate very rough and uneven terrain. Farming vehicles often transport heavy loads such as fertilizer, seeds, and liquids for spreading or spraying, often times carrying heavy weights high above the vehicle's center of gravity. In order to maintain vehicle stability with these heavy loads, it is important that all four wheels contact the ground continuously while the vehicle frame, and thus, the load maintain level travel.
Suspension systems utilizing a trailing arm portion to absorb vehicle motion forces are commonly known. For example, U.S. Pat. No. 2,510,424 to Shook is directed to a suspension comprising two trailing arms hinged at one end to a substantially U-shaped laterally tiltable member. The trailing arms are hinged at the other end to a housing located at the inner sides of the wheels. There are separate axles journaled in a housing. The housing is pivotally attached to the center of a crossbar. The trailing arms connect to the U-shaped member at a level well above the connection to the axle. This high angle of attachment imposes greater sheer stress on the pin connecting the trailing arm to the U-shaped member than would a trailing arm positioned in a plane substantially parallel to level ground.
U.S. Pat. No. 3,426,862 to Wilfert relates to a drive axle for vehicles, the relevant part comprising two trailing arms rotatably connected at one end by pins to a transversely disposed tubular shaped housing. The housing is rigidly connected in a cross-like manner with another tubularly shaped housing part that is pivotal about the vehicle longitudinal axis. The second tubular shaped housing supports the drive axle and the trailing arms are secured at the other end to the wheel carriers. Guide links above and below the driving half shafts are used as cross-guide members, while the axle gear is rigidly or elastically mounted to the frame. These joints where the two housings connect are more likely to weaken and/or fail than would a one-piece unit.
What is needed is a suspension system that minimizes stress on the connecting points, while allowing all four vehicle wheels to independently maintain contact with the ground and simultaneously keep the vehicle frame level, thereby permitting increased weight loads to remain stable while traversing uneven terrain.